2 // Start the level (use 1.2 to make it easy). Have the host hand items (Rotten Eggs, First Aid, Ammo) off to the guest for duplication.

3 // With a full inventory, have the guest leave the game (it should say "All unsaved progress will be lost" -- select "Yes").

5 // After selecting "Yes," another question for the guest will appear asking whether or not to save status and ammo. Choose "Yes" to save and you will have all the passed-on inventory saved.

6 // Now, back to the host: Quit out of the game, but at the second question, choose "No" and do not save ammo and status.

7 // Restart the game with the two characters and you'll both have the ammo and items. Duplication successful! (Note: You cannot do this with weapons as you cannot hand them off to your partner.)

Addendum: A popular money-making strategy involves duplicating Gold or Rotten Eggs. These are worth $2,000 a pop, and 5 can be crammed in each inventory slot. That means you can eventually be duplicating $90,000 each time. Finding Rotten Eggs can be tough; they drop randomly from enemies in later levels. Also, for two people to increase the amount of eggs quickly, you'll have to pass them back and forth, alternating who is saving and who isn't. Finally, you may request eggs from the computer once the guest has quit out to make this process faster.